Insulin Reaction

Reviewed on 9/10/2021

What Facts Should I Know about Insulin Reaction?

Insulin Reaction
Insulin is a hormone (a chemical substance that acts as a messenger in the human body) that is secreted by an abdominal organ called the pancreas. High insulin levels are levels of the hormone that are higher than they should be after ingesting glucose.

What is the medical definition of insulin reaction?

An insulin reaction occurs when a person with diabetes becomes confused or even unconscious because of hypoglycemia (hypo=low + glycol = sugar + emia = in the blood) caused by insulin or oral diabetic medications. (Please note that for this article blood sugar and blood glucose mean the same thing and the terms may be used interchangeably.)

The terms insulin reaction, insulin shock, and hypoglycemia (when associated with a person with diabetes) are often used interchangeably.

What happens if you have too much insulin in your body?

In normal physiology, the body is able to balance the glucose (sugar levels) in the bloodstream. When a person eats, and glucose levels start to rise, the body signals the pancreas to secrete insulin. Insulin "unlocks the door" to cells in the body so that glucose can be used for energy. When blood sugar levels drop, insulin production decreases and the liver begins producing glucose.

In people with diabetes, the pancreas is unable to produce enough insulin to meet the body's demand. Treatment may include medications taken by mouth (oral hypoglycemics), insulin, or both. The balance of food intake and medication is not automatic, and a person with diabetes needs to be aware that too much medication or too little food may cause blood sugar levels to drop.

Interestingly, brain cells do not need insulin to access the glucose in the bloodstream. Brain cells also cannot store excess glucose, so when blood sugar levels drop, brain function is one of the first parts of the body to become affected.

In an insulin reaction, the blood sugar levels are usually below 50 mg/dL (or 2.78 mmol/L in SI units).

What Causes Insulin Reaction?

Insulin reactions occur when there is an imbalance of food intake and the amount of insulin in the body. Oral hypoglycemic medications can remain active in the body for more than 24 hours. The effects of Injectable insulin can be short or very long depending upon the type. Even in individuals whose diabetes is well controlled and regulated with medication, a variety of factors can cause the insulin/glucose levels to fluctuate from the normal range. Also, alcohol plays a role in causing hypoglycemia?

People who have had diabetes for 10-20 years and/or have been on long term or large doses of insulin are more prone to "insulin unawareness". They can suddenly become hypoglycemic without any warning and should check sugar before driving. They should consider Continuous Glucose Monitoring or a handheld reader with a 14-day patch that lets them read blood sugar at any time.

Perhaps the most common cause of an insulin reaction or hypoglycemia is a missed meal. Once insulin is injected or a diabetes medication is taken, its effect needs to be balanced by caloric intake from food (providing glucose to bind with the insulin). If the number of calories eaten decreases, blood glucose levels drop and the insulin acts unopposed, which causes the characteristic symptoms of an insulin reaction. An insulin reaction can also occur with exercise. When a person exercises the muscle cells need extra energy (glucose), and if food intake is decreased, the blood sugar levels will drop.

Another common cause of insulin reaction is medication error. If a person with diabetes injects too much insulin or takes too many diabetic drugs, the insulin levels in the blood rise because there is not enough glucose in the blood to bind to the insulin, and an insulin reaction occurs.

Disorders of these endocrine glands can also affect the balance between insulin and glucose in the body.


Diabetes is defined best as... See Answer

What Are the Symptoms of Insulin Reaction?

The symptoms of an insulin reaction are due to decreased brain cell function because of lack of glucose within the bloodstream. The longer the hypoglycemia persists, the more severe the symptoms.

Mild Symptoms of Insulin Reaction

Moderate Symptoms of Insulin Reaction

Severe Symptoms of Insulin Reaction

  • unconsciousness
  • seizures
  • coma
  • stroke like symptoms
  • hypothermia (low body temperature) may occur if the hypoglycemia persists for a prolonged period of time

What Is a Nocturnal (While Asleep) Insulin Reaction?

Some people with diabetes experience nighttime (nocturnal) hypoglycemia. Signs and symptoms of nocturnal hypoglycemia include:

In nocturnal hypoglycemia, the blood sugar level upon awaking may be elevated as a result of the body's attempt to compensate for the low blood sugar level several hours before. This is sometimes called the Somogyi phenomenon. Attempts to lower the morning blood sugar level by adjusting mediation or insulin dosing may result in a paradoxical worsening of the problem.

Insulin Reaction Times

Onset of signs and symptoms is generally sudden and within a few hours after injection of short-acting insulin. The onset may occur many hours after injection of long-acting insulin preparations or with oral medications. In this case it may be more difficult to appreciate the symptoms as being related to hypoglycemia.

When to Seek Medical Care for an Insulin Reaction

Most people with diabetes have experienced an insulin reaction early after their initial diagnosis as diet and medication or insulin dosing are being adjusted to fit into their lifestyle.

Whenever a person is unconscious, regardless of the cause, call 911 or your local emergency telephone number to activate emergency medical service responses.

If the affected individual remains confused, even after eating or drinking to correct low blood sugar, he or she should receive medical care.

People with diabetes who take sulfonylurea oral hypoglycemic medications, like glipizide (GlipiZIDE XL, Glucotrol, Glucotrol XL), glyburide (DiaBeta, Glynase PresTab, Micronase), or glimepiride (Amaryl), should contact their health care practitioner or seek urgent medical care if they experience an insulin reaction. These medications can remain active in the body for a prolonged period of time, and observation in a hospital setting may be necessary.

Insulin reactions, especially those that occur at night or early morning should be reported to your health care practitioner. People with diabetes should keep a record of their blood sugar readings as it is an important tool to help keep blood sugars under a good control and decrease the risk of long-term complications of diabetes.

How Is an Insulin Reaction Diagnosed?

A low blood sugar associated with symptoms of hypoglycemia confirms an insulin reaction.

The next step is to find out why the insulin reaction occurred. The history is taken by the health care practitioner from the patient, bystanders, and family. Often those people that were around the affected individual can assist in defining the reason for the reaction. Further testing and follow-up will depend upon the situation. A person who wakens immediately and returns to normal function with correction of the blood sugar may need no further testing. An individual who continues to have mental status changes like confusion, lethargy, coma, or stroke-like symptoms will likely require further care and testing.

What Is the Medical Treatment for Insulin Reaction?

Increasing blood sugar levels is the treatment of an insulin reaction. Emergency personnel may start an intravenous line and inject an ampule of D50W, a highly concentrated glucose solution. If the patient takes a long-acting insulin or oral hypoglycemic medication, the IV line may be left in place and a dextrose (a type of sugar) solution may be continually infused.

Patients who are elderly, have an underlying illness that caused the hypoglycemia, or are taking long-acting medication may need further observation, additional treatment, and admission to the hospital.

Patients who are cold (hypothermic) because of a prolonged insulin reaction may require rewarming.

Most patients are able to be discharged home after a short observation period. When EMS is involved at home, if the patient wakens and returns to normal with glucose treatment, there may be no need to transport them to hospital if there is a responsible adult who can care for them at home.

Self-Care at Home for Insulin Reaction?

Most people with diabetes or their family members can recognize the early symptoms of an insulin reaction and can self-treat the situation. Ideally, a fingerstick blood test will be taken to confirm the diagnosis, but it is also reasonable to immediately drink something with sugar (for example, fruit juice, regular soda, or water with table sugar). Glucose tablets and sugar wafers are also easily digested and can provide instant glucose into the bloodstream.

Emergency medical services (call 911 or your local emergency number) should be activated if the affected person is unconscious or has difficulty staying awake. Do NOT try to put food or drink into an unconscious person's mouth because there is a risk that it will be aspirated into the lungs causing pneumonia.

It is reasonable to try to rub sugar or another sweet substance inside the cheek or along the gum line. Sugar is quickly absorbed through these sites, and this may be enough to wake the patient.

Glucagon is an injectable medication that can raise blood sugar levels. Many people with diabetes carry an injectable glucagon pen to use in emergencies, and often their family members also are trained in how to give an injection to treat low blood sugar levels. The patient cannot always realize that the reaction is happening and his/her relatives should be taught when and how to inject Glucagon. After a Glucagon injection, people are subject to an even worse reaction and they should try to ingest sugar as soon as they come out of the initial reaction.

Should the affected individual return to normal, fingerstick blood sugar tests should be checked regularly (every 15-20 minutes) to make certain that the levels do not start to drop again. The person should not be left alone in case of hypoglycemia recurs.

How Do You Prevent Insulin Reaction?

People with diabetes need to be vigilant to maintain their blood sugar levels within the normal range. Diet, exercise, and proper insulin dosing need to be continually monitored to prevent hypoglycemia and insulin reactions.

What Is the Prognosis for an Insulin Reaction?

  • Insulin reactions are a common situation and are usually easily treated with little consequence.
  • If the episode occurs when the patient is driving, using heavy machinery, or otherwise engaged in a potentially risky situation, an injury may occur.
  • Patients may develop significant organ damage if blood sugars remain low for a prolonged period of time.


Diabetes: What Raises and Lowers Your Blood Sugar Level? See Slideshow

Health Solutions From Our Sponsors

Reviewed on 9/10/2021
Medically reviewed by John A. Seibel, MD; Board Certified Internal Medicine with a subspecialty in Endocrinology & Metabolism


Fauci, Anthony S., et al. Harrison's Principles of Internal Medicine. 17th ed. United States: McGraw-Hill Professional, 2008.

Patient Comments & Reviews

  • Insulin Reaction - Patient Experience

    Did you have an adverse action to insulin? Please tell us about your experience.